Spinnerette



Feb; 7, 1967 F. J. MEDEIROS 3,302,238

- SPINNERETTE Filed Feb. 10, 1965 2 Sheets-Sheet 1 Feb. 7, 19 67 F. J. MEDEIROS SPINNERETTE 2.Sheets-Sheet 2 Filed Feb. 10, 1965 United States Patent 3,302,238 SPINNERETTE Francis Joseph Medeiros, Hendersonville, Tenn., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Feb. 10, 1965, Ser. No. 431,688 3 Claims. (Cl. 18-8) This invention relates to the spinning of molten, organic filament-forming compositions and more particularly to a spinneret design therefor.

It has been customary in the melt-spinning of organic polymeric materials to use spinnerets with a circular aperture-pattern to produce round strands of filaments. The circular pattern is a preferred design because it can be used with radial quenching which provides uniform cooling with good filament stability in the quench chimney, The round strands produced with circular-aperture-pattern spinnerets are very suitable for conversion to continuous filament yarns, or by blending with additional similar strands, for formation of thick tows for subsequent crimping and other operations.

In accordance with the present invention a multifilament strand is spun having the filaments therein so disposed as to be eminently suitable for the economical commercial manufacture of nonwoven webs using the recently-developed web-laydown process described in British Patent 932,482. In this process, which utilizes an integrated filament-spinning, attenuation and web-laydown operation, a multifilament strand of freshly spun, continuous filaments is electrostatically charged under tension, for example, by passing the filaments through a corona discharge zone; the charged filaments are then forwarded by means of a jet device towards a web-laydown zone; and tension on the filaments is released as they exit the jet device; thereby permitting them to separate due to the applied electrostatic charge; and the filaments, while thus separated, are collected as a nonwoven web.

In the step of application of an electrostatic charge to filaments by triboelectric charging or by the corona discharge technique described in DiSabato & Owens, U.S. Patent 3,163,753, the filament strands are contacted with cylindrical target bars. The corona discharge technique is a preferred method because it permits the application of a uniform, high level of charge to each of the multifilament strands.

In order to prepare wide webs economically by the aforementioned integrated process, it is necessary to use the output from a plurality of spinnerets. This in turn makes it necessary to use mechanical attenuation of the filaments, for example, with draw rolls, in order to obtain uniform filament properties from each of the spinnerets and, therefore, uniform properties throughout the nonwoven web.

In the production of nonwoven webs by the abovedescribed integrated process, it has now been found that the filaments must be spaced from one another in the strand in a designated relationship in order to obtain uniform webs which are free from aggregates or bundles of filaments. While this distribution is very important in the matrix filament strands which make up the predominant or entire filamentary structure of the nonwoven web, it is particularly required when binder filaments are spun and then blended with the strands of matrix filaments before web-laydown. This method for distributing the binder throughout the nonwoven web requires complete and uniform separation of the binder filaments before they are added to the matrix filaments. Without this type of separation, matrix and binder filaments will not be uniformly blended and, accordingly, the binder will not be uniformly distributed throughout the nonwoven web. Strands issuing from spinnerets with a circular aperturepattern have been found to result in webs of less desired uniformity when the above-described integrated process is employed.

It is the purpose of this invention to provide a spinneret design for the production of a multifilament strand which can be converted into uniform nonwoven webs.

This and other purposes are attained in accordance with this invention by providing a spinneret with spinning apertures arranged on a plurality of ellipses having a common major axis. The apertures are spaced on the ellipses so that the horizontal distance between adjacent apertures on each ellipse is constant and the horizontal distance between adjacent projections of all the apertures onto the major axis is constant. By horizontal distance is meant that vec tor of the distance which is parallel to the major axis.

In order to obtain as nearly uniform polymer flow to each aperture as possible and to minimize areas where polymer can accumulate and degrade, the lengths of the minor axes of the ellipses are adjusted to have the relationship with the major axis and the number of ellipses represented in the following equation:

where D is the length of the minor axis of ellipse N;

N is the ellipse number, where the ellipses are numbered consecutively (l, 2, 3, etc.) starting with the ellipse having the smallest minor axis;

E is the total number of ellipses; and

D is the length of the major axis.

The number of ellipses used in the design is determined by the number of holes desired and the minimum allowable distance between holes (about 0.1 in.; 0.25 cm.). The maximum length of the major axis is determined by the internal diameter of the spinneret pack gasket.

The spinneret design of the invention permits ready quenching of the filaments by directing the gaseous cooling medium (for example, air) either in the same direction as the major axis or perpendicular to it. The latter method is particularly effective because the cooling medium has ready access to all the filaments. The spinneret design is also particularly well adapted to radial quenching which provides uniform, effective cooling with good filament stability in the quench chimney.

FIGURES 1 and 2 are plan views, on an enlarged scale, of specific embodiments of the spinnerets of this invention. FIGURE 1 shows a spinneret with 51 apertures arranged on two ellipses, and FIGURE 2, a spinneret with 82 apertures arranged on three ellipses. The uniform spacing of the projections of these apertures on a line parallel to the major axis is indicated at A in each figure. These specific designs are suitable for spinnerets in which the maximum length of the major axis is 2.125 in. (5.40 cm.). In FIGURE 1 the individual horizontal spacing of the 51 apertures, when projected onto the major axis, 'is 0.0425 in. (0.118 cm.); in FIGURE 2, the individual horizontal spacing of the 82 apertures is 0.025 in. (0.0635 cm.). During use in the web-laydown process described above, each spinneret is positioned with its major axis parallel to the axes of the rotating guide members which convert the strand of filaments to a fiat ribbon, thus the major axis is parallel to the plane of the ribbon of filaments.

A nonwoven web is produced by the above-described, integrated web-laydown process using a series of 250-aperature spinnerets with circular aperture patterns to spin matrix filaments of poly(ethylene terephthalate) and an equal number of Sl-aperture spinnerets, as in FIGURE 1, to spin binder filaments of a 79/21 copolymer of poly- (ethylene terephthalate) poly (ethylene isophthalate The outputs from the 5l-apertu1'e spinnerets are in the form of elliptical patterns with a common major axis and are converted to individual ribbons of filaments by contact with appropriate guide surfaces and draw rolls. Each ribbon of binder filaments is spread by means of convex guides to a Width of 4.5 in. (11.4 cm.), While each ribbon of matrix filaments is converged by means of concave guides to a width of 4.5 in. (11.4). The ribbons are separately electrostatically charged by corona-discharge devices positioned between the spinnerets and draw rolls. A ribbon of binder filaments is then uniformly distributed through each ribbon of matrix filaments and the composite ribbons are then directed toward the weblaydown zone by filament-forwarding slot-jet devices. The jet devices are positioned to give 67% overlap between the laterally-adjacent areas of deposition of the filaments on a moving web-laydown receiver. Suction is applied beneath the receiver in the web-laydown zone to pin the filaments to the receiver and to counteract the aerodynamic and electrostatic interference between the outputs from adjacent jets. The binder distribution across the nonwoven web is then determined. For comparison, a similar web is prepared using a 40-aperture spinneret with a circular aperture-pattern to spin the binder filaments. The results of the binder-distribution measurements are summarized below and indicate that a significantly better binder distribution is obtained with the elliptical aperturepattern.

In addition, the stability of the filaments in the quench zone, the separation and stability on the guide surfaces, and the separation of the binder filaments in the nonwoven web are much improved with the elliptical-aperture pattern.

What is claimed is:

1. A spinneret plate having spinning apertures arranged in a plurality of substantially elliptical patterns with a common major axis, the distance between adjacent apertures on each elliptical pattern as measured by the distance between projections of the apertures onto the major axis being substantially equal and the distance between adjacent projections of the apertures of all the elliptical patterns onto the major axis being substantially equal.

2. The spinneret plate of claim 1 wherein the lengths of tthe minor axes of the elliptical patterns are determined by the following formula:

where D is the length of the minor axis of ellipse N;

N is the ellipse number, where the ellipses are numbered consecutively l, 2, 3, etc.) starting with the ellipse having the smallest minor axis;

E is the total number of ellipses; and

D is the length of the major axis.

3. A spinneret according to claim 1 having fifty-one spinning apertures arranged in two substantially elliptical patterns.

References Cited by the Examiner UNITED STATES PATENTS 1,603,813 10/1926 Stein 18-13 X FOREIGN PATENTS 932,482 7/1963 Great Britain. 957,534 5/1964 Great Britain.

WILLIAM J. STEPHENSON, Primary Examiner.

ROBERT F. WHITE, Examiner.

R. B. MOFFITT, Assistant Examiner. 

1. A SPINNERET PLATE HAVING SPINNING APERTURES ARRANGED IN A PLURALITY OF SUBSTANTIALLY ELLIPTICAL PATTERNS WITH A COMMON MAJOR AXIS, THE DISTANCE BETWEEN ADJACENT APERTURES ON EACH ELLIPTICAL PATTERN AS MEASURED BY THE DISTANCE BETWEEN PROJECTIONS OF THE APERTURES ONTO THE MAJOR AXIS BEING SUBSTANTIALLY EQUAL AND THE DISTANCE BETWEEN ADJACENT PROJECTIONS OF THE APERTURES OF ALL THE ELLIPTICAL PATTERNS ONTO THE MAJOR AXIS BEING SUBSTANTIALLY EQUAL. 